Computer Science
Scientific paper
Sep 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995metic..30q.513g&link_type=abstract
Meteoritics, vol. 30, no. 5, page 513
Computer Science
2
Calcium-Aluminum-Rich Inclusions, Fassaite, Micrometeorites, Perovskite, Rare Earth Elements
Scientific paper
Refractory inclusions are charcteristic components in carbonaceous chondrites. Therefore, refractory inclusions found in micrometeorites can give important hints about the relationship between micrometeorites and carbonaceous chondrites. So far, only a few inclusions were found in micrometeorites [1-4]. In this study we report the first trace element analysis of perovskite and fassaite found in micrometeorites. We studied two Antarctic micrometeorites by ASEM, EMP, and SIMS. The first particle is 120 micrometers in size mainly consisting of a fine-grained matrix of dehydrated former phyllosilikates that enclose a 5 micrometers sized perovskite [5]. The perovskite is surrounded by a 1 micrometers thick rim of ilmenite and contains up to 1.3 wt% FeO as determined by EMP. The trace element abundances were determined by SIMS following the procedure described by [6]. The REE pattern of the perovskite is shown in Fig. 1. The pattern is closely related to the Group II pattern with its typical depletion of the more refractory REEs [7]. It is also very similar to the REE abundances of perovskite from Murchison (CM) [8] and CH-chondrites [9]. This may indicate a relationship between this micrometeorite and components in carbonaceous chondrites. The second micrometeorite is 100 micrometers in size consisting of a fine-grained (20 micrometers across) and a coarse-grained (80 micrometers across) area. Both areas contain fassaite with different chemical compositions. The particle was previously analyzed by Lindstrom and Kloeck [1] without knowing the mineralogy. We carried out SIMS analysis of each area of the micrometeorite separately. The TEE patterns of these two areas are similar and show in general a Group III pattern (20-30x CI) in which the more refractory REEs are not fractionated. The negative Eu anomaly is much more apparent in the coarse-grained area and no Yb anomaly is apparent in one of the areas. This is the first CAI of a micrometeorite showing a Group III REE pattern. References: [1] Lindstrom D. J. and Kloeck W. (1992) Meteoritics, 27, 250. [2] Kurat G. et al. (1994) Meteoritics, 29, 487-488. [3] Kurat G. et al. (1995) LPS XXV, 763-764. [4] Hoppe P. et al. (1995) LPS XXVI, 623-624. [5] Beckerling W. et al. (1992) Meteoritics, 27, 200-201. [6] Zinner E. and Crozaz G. (1986) Int. J. Mass. Spectr. Ion Processes, 69, 17-38. [7] Martin P. and Mason B. (1974) Nature, 249, 333-334. [8] Ireland T. et al. (1988) GCA, 52, 2841-2854. [9] Weber et al. (1995) GCA, 59, 803-823.
Bischoff Addi
Greshake Ansgar
Hoppe Peter
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